Light emitting diode assembly

ABSTRACT

Light emitting diodes are mounted in an assembly of electrical leads and lenses, the leads having a common carrier strip attached thereto and pairs of resilient contact fingers, the diodes being resiliently gripped between pairs of contact fingers and then encapsulated in a light transmitting material which itself forms a diffusing lens; a separate lens alternatively being provided by a rigid outer shell of light transmitting material.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 330,925, filedDec. 15, 1981, now abandoned, which is a continuation of applicationSer. No. 102,308, filed Dec. 11, 1979, now abandoned, which is adivision of application Ser. No. 883,559, filed Mar. 6, 1978, now U.S.Pat. No. 4,247,864, which is a continuation-in-part of Application Ser.No. 816,423, filed July 18, 1977.

BACKGROUND OF THE PRIOR ART

U.S. Pat. No. 4,012,608 is representative of the prior art wherein alight emitting diode is provided with electrical leads for incorporationinto an electrical circuit component of miniature size such as amanually actuated switch. The diode is incorporated into the electricalcircuit of the switch by slender and delicate electrical leads which arebonded to the diode. A more rugged diode connection is taught in U.S.Pat. No. 3,999,287 wherein the diode leads are comprised of resilientmetal strips. A diode is press fitted between the metal strips and thenencapsulated in place. The present invention relates to an improvedstructure and method providing a diode assembly.

BRIEF DESCRIPTION

The present invention relates to light emitting diode (LED) assemblies,and more specifically, to assembly of light emitting diodes with lensesand electrical leads. A series of stamped and formed electrical leadsare provided along a carrier strip. The leads include resilient fingerswhich project outwardly of the plane of the carrier strip. The fingersare resiliently deflected to spread apart configurations. Properlyoriented LED's are positioned between the fingers. Subsequently, thefingers resiliently grip opposite sides of the diodes, making electricalconnections therewith, and positioning the diodes in a plane elevatedfrom the carrier strip. The diodes, together with at least portions ofthe fingers, are encapsulated in a solidifiable and light transmittingmaterial advantageously molded into a desired lens configuration.Alternatively, the diodes may be located in corresponding cavities of arigid shell of light transmitting material. The diodes are thenencapsulated with a light transmitting encapsulant which also fills thecavity of the lens shell. What results is a series of encapsulateddiodes arranged in strip form already provided with light diffusinglenses and electrical leads. The diode assemblies then are capable ofseparation from the carrier strip individually or in groups forincorporation within an electrical circuit, the leads beingadvantgeously used as solderable tabs or pluggable electrical leads.

The encapsulant is provided with a concave outer surface which iscovered or coated with a reflective material such as paint containingtitanium oxide. Light emission from the LED in the encapsulant isretroreflected thereby. If the encapsulant, or the outer lens, includesa convex outer surface, by viewing the light emission through suchsurface, the retroreflected light, combined with the remainder of lightemission, will become magnified when emitted through the surface toappear unusually bright.

In another form of the invention, the finger portions project from oneside of the carrier strip and are bent outwardly of the plane of thecarrier strip. Two sections of carrier strip are positioned so that thefingers of one strip partially overlap corresponding fingers of theother strip. The fingers are resilient and thereby tend to spring back aslight amount toward the plane of the carrier strip after being bent.This action biases the overlapping portions of the fingers toward eachother into gripped engagement on a diode.

According to another embodiment of the invention a pair of diodes areengaged by and between a pair of electrical leads, each lead being ananode for one diode and a cathode for the other diode. If the diodes areLED's which emit light of different colors, the polarity of voltageimpressed across the leads is indicated by the corresponding coloremitted by the conducting LED.

OBJECTS

It is therefore an object of the present invention to provide a diodemounting assembly comprising a series of electrical conducting contactshaving resilient fingers and electrical leads, the fingers beingresiliently biased apart to receive diodes therebetween, the fingersresiliently gripping opposite sides of the diodes in elevated positionssuitable for encapsulation in a light transmitting encapsulant material.

Another object of the present invention is to provide a method forfabricating a light emitting diode assembly by providing a series ofstamped and formed electrical leads having resilient finger portionswhich grip diodes inserted between pairs of the fingers, the grippeddiodes being encapsulated together with portions of said fingers in alight transmitting encapsulant material, alternatively provided with arigid light transmitting lens.

Another object of the present invention is to provide an assemblywherein two LED's having light emissions of different colors areconnected between a pair of electrical leads, the color of light emittedby the conducting LED indicating polarity of a voltage impressed acrossthe leads.

Other objects and many attendant advantages of the present inventionwill become apparent from the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged fragmentary perspective of a series of electricalcontacts mounted along a pair of common carrier strips particularlyillustrating the contacts as having projecting pairs of resilient fingerportions;

FIG. 2 is an enlarged front elevation of a typical lead assembly of FIG.1 showing depending leads and elevated resilient fingers inclined towardeach other.

FIG. 3 is an enlarged fragmentary side elevation of the embodiment ofFIG. 2 taken along the line A--A.

FIG. 4 is a view similar to FIG. 2 illustrating diode insertion betweenpairs of fingers.

FIG. 5 is an enlarged elevation of the embodiment shown in FIG. 4 withthe inserted diode being inverted and encapsulated in a lighttransmitting material.

FIG. 6 is an enlarged fragmentary perspective of a lens shell having aseries of individual lenses connected integrally together and providedwith a series of cavities.

FIG. 7 is an enlarged elevation of the embodiment shown in FIG. 4 withthe inserted diode inverted and received in a corresponding cavity ofthe lens shell illustrated in Fig. 6.

FIG. 8 is an enlarged front elevation in section of an alternative diodeassembly wherein a diode together with the gripping fingers areencapsulated in a light transmitting material which in turn fills acavity of the lens shell.

FIG. 9 is an enlarged fragmentary perspective of another embodiment ofelectrical contacts.

FIG. 10 is an enlarged fragmentary plan of the embodiment illustrated inFIG. 9.

FIG. 11 is an enlarged fragmentary elevation in section of theembodiment as shown in FIG. 10.

FIG. 12 is a section taken along the line 12--12 of FIG. 10.

FIG. 13 is an enlarged fragmentary perspective of another embodiment ofanLED assembly incorporating the contacts of FIG. 9 in an outer shell.

FIG. 14 is a section taken along the line 14--14 of FIG. 13.

FIG. 15 is an enlarged fragmentary elevation of a polarity indicatingLED assembly.

FIG. 16 is a fragmentary plan taken along the line 16--16 of FIG. 15.

DETAILED DESCRIPTION

With more particular reference to the drawings, there is shown in FIG. 1generally at 1 a preferred embodiment of a diode mounting frameworkcomprising a series of electrical contacts 2 which are stamped andformed out of metal strip and which include corresponding pairs ofdepending electrical leads 4 integral with corresponding pairs ofvertically projecting resilient electrical contact fingers 6. Thecontact fingers are arranged in opposed pairs with opposed fingers beinginclined toward each other. The free ends 8 of the contact fingers arearcuately bowed or flared away from each other. The other ends of thefingers are connected to web portions 10 which project laterally frominterconnecting and integral strips 12. The strips 12 connectcorresponding contacts 2 integrally with carrier strips 14, along withthe series of contacts 2 are arranged in serial fashion. Each of thewebs 10 is provided with a lateral opening 16 which passes under opposedcontact fingers 6 and which separates the lower ends of the fingers 6from each other. Each opening 16 also is interposed betweencorresponding pairs of leads 4 separating them from each other.

With reference to FIGS. 3 and 4, insertion of the diodes will bedescribed in detail. Each corresponding pair of fingers 6 projectvertically outward from the common plane of the carrier strips 14 andare spaced apart to define a triangular shaped opening or clearancetherebetween. Each pair of fingers 6 are also inclined from the verticalas shown in FIG. 3. A toolhead is shown schematically at 18. Thetoolhead includes a projecting shaft 20 which carries an eccentricallymounted cam lobe 22. The tool is slidably advanced along and inregistration against an edge margin 19 of the strip 12 that extends fromone carrier strip 14 to the other, thereby to position the cam lobe 22in the opening or clearance between a corresponding pair of fingers 6.As shown in FIG. 4, the initial position of the lobe 22 is verticallybelow the shaft 20. The lobe is then pivoted about the shaft to itsposition vertically above the shaft 20 where it engages the undersidesof both fingers 6, spreading apart the free ends 8 thereof. Moreparticularly, the arms 6 are resiliently deflected away from each otherby the cam lobe 22. This allows for receipt of an LED chip 24 betweenthe spread apart free ends 8. Insertion of the LED is accomplished by apincer type toolhead 26. The LED 24 is fully inserted when placed inregistration against the top surface of the cam lobe 22 as shown in FIG.4. Subsequently, the cam lobe 22 is pivoted to its FIG. 3 outlineposition disengaged from the fingers 6 allowing them to resilientlydeflect by residual spring action toward each other whereby the freeends 8 grippingly engage opposite sides of the inserted diode 24 makingelectrical contact therewith and mounting the diode to the electricalcontact 2. The diode may then be released by the toolhead 18. Inpractice, the toolhead 26 and the toolhead 18 are components of anassembly machine which automatically actuates the cam lobe and insertionhead in the sequence of insertion as described. Each corresponding pairof fingers 6 are indexed forwardly into position by proper indexing ofthe carrier strips 14, followed by repeated sequencing of the toolheads26 and 18. Alternatively, multiple stations having toolheads 18 and 26may be provided for multiple simultaneous LED insertion. What results isan array of diode assemblies serially located along the carrier strips14 and comprising diode chips grippingly engaged between correspondingfingers 6.

FIG. 5 illustrates schematically encapsulation of the inserted LED's.More particularly, the LED's 24 are sufficiently gripped betweencorresponding fingers 6 to allow the assemblies to be inverted withoutdislodging the inserted LED's. The inverted LED's are then dipped orotherwise located within corresponding cavities 28 of a suitable mold30. A quantity of a light transmitting encapsulant material 32 is thendeposited in each mold cavity 28. Upon solidification of the encapsulantmaterial, the LED 24, together with at least the portions 8 of thefingers 6, are encapsulated within corresponding globules ofencapsulant. Upon removal of the solidified encapsulant globules fromthe mold 30, what results is a series of encapsulated LED's seriallyalong the carrier strips 14, with the solidified encapsulation material32 associated with each LED being molded to a desired shape and forminglight diffusing lenses. The remainder of the fingers 6 and the leads 4project from the encapsulant material to establish electrical connectionpoints. The encapsulant may be of the type which solidifies, such aslight transmissive epoxy, for example. Solidification of the encapsulantrigidly retains the contact fingers and the diodes in place, with thecontact fingers retained in pressure contact with the diodes sufficientto establish pressure electrical connections. Removal of the carrierstrips 14 and bridging members 12 allow isolation of individual diodestogether with accompanying electrical leads 4.

FIGS. 6-8 illustrate another preferred embodiment according to thepresent invention. As shown in FIG. 6, a molded lens shell generallyindicated at 34 is molded into the shape of a series of bulbous lenses36 integrally connected together and provided with individual lenscavities 38 in each of the lenses 36. As shown in FIG. 7, the serialarray of LED's 24 are shown inverted together with their carrier strips14 and arms 6. The serial array of LED's 24 are located withincorresponding serial arrayed lens cavities 38 and a quantity of lighttransmitting encapsulant material 40 is deposited within each of thecavities 38. Upon solidification of the encapsulant material 40 theLED's 24 together with at least portions of the arms 6 are encapsulatedwithin the shell 34. The shell 34 thus provides the desired lens shapefor the LED's 24. A multiple number of LED's 24 may be provided in thelens shell 34. Alternatively, the shell 34 may be divided as desired toprovide individual ones, or any selected number of LED's in a singlelens assembly wherein each of the LED's 24 is provided with electricalleads 4 which project outwardly of the lens shell for pluggable orsolderable connection of the LED's to circuitry.

FIGS. 9-12 illustrate another embodiment of a diode mounting frameworkgenerally illustrated at 42 and comprising a series of electricalcontacts 44 which are stamped and formed out of the strip and whichproject laterally from a common integral carrier strip 46. Each of thecontacts 44 includes an electrical lead 48 frangibly connected to thestrip 46. Each contact 44 further includes a resilient electricalcontact finger 50 which is bent at 52 to project outwardly of the planeof the metal strip from which the carrier strip 46 and contacts 44 arefabricated. Each contact finger portion 50 is interconnected to adjacentfinger portions 50 by integral support strips 54 which extend generallyparallel to the carrier strip 46. As shown in FIGS. 9 and 10, anothersection of a diode mounting framework is illuatrated at 42' identical tothe section of framework illustrated at 42. The framework section 42'includes a carrier strip 46' from which project integral contacts 44'having the corresponding electrical leads 48', the contact fingerportions 50', and the auxiliary support strips 54'. The strip sections46 and 46' are positioned opposite each other as shown such that eachcontact finger portion 50 overlaps a corresponding contact fingerportion 50'. More particularly, the free end of each contact finger 50includes a metal plate portion 56 overlapping, in side-by-siderelationship, a similar plate portion 56' provided at the free end of acontact finger portion 50'. The finger portions 50 and 50' arefabricated from resilient metal strip and thereby tend to return to theplane of the corresponding strip 46 and 46' after being bent at 52 and52'. This return action, or spring back action, resiliently biases theplate portions 56 and 56' toward each other in order to resilientlyengage on either side of at least one diode or LED 58 sandwiched betweenthe plate portions 56 and 56'.

To insert one or more of the diodes 58, the carrier strip sections 46and 46' are placed upon a fixture (not shown) and adjusted in positionon the fixure until the plate portions 56 and 56' are in desiredoverlapped alignment and are positioned, either in compression againsteach other, or spaced apart with a small clearance as desired. The stripsections 46 and 46' may be then clamped by any suitable clampingapparatus to the fixture. Suitable insertion heads, such as used in thepreviously described embodiment, are provided to bias apart the plateportions 56 and 56', and to insert at least one diode 58 therebetween.Such insertion heads may be of the type previously described withrespect to the embodiment shown in FIGS. 3 and 4. The plate portions 56and 56' will resiliently engage the inserted LED 58. Subsequently,solder may be applied to solder the LED 58 to each of the plate portions56 and 56'. It is, however, more advantageous to coat the plate portions56 and 56' with a quantity of adhered solder prior to assembly on thefixture as described. As shown in FIG. 12, such a solder coating 60 willelectrically secure the diode 52 to the plate portions 56 and 56' whenthe solder is, first, reflowed upon the application of heat andsubsequently, when cooled, the solder coating 60 will solidify andpermanently secure the contacts 56 and 56' to opposite sides of thediode 58. Thereby, the contacts 56 and 56' provide an anode and cathodeconnection for the diode 58. What results is a series of LED assemblies63 arranged serially like rungs of a ladder interconnected between thestrip sections 46 and 46'.

FIGS. 13 and 14 illustrate a molded lens shell illustrated generally at62, molded into a series of individual bulbous lenses 64 which arespaced apart and interconnected by pairs of molded webs 66. Lenses 64are spaced apart a distance equal to the LED assemblies 63 spaced alongthe carrier strip sections 46 and 46'. Each LED assembly 63 is receivedwithin an internal cavity 68 of a corresponding lens 64 as shown in FIG.14. Each cavity 68 is then at least partially filled with a lighttransmitting encapsulant material 70 which is subsequently solidified toembed the LED 58 and portions of the contacts 50' and 50 within thecavity 68. The lead portion 46 and 46' project outwardly of theencapsulant material in the lens cavity 68 to establish solderable tabsor pluggable electrical leads. The leads 46 and 46' may be bent to anydesired orientation. The auxiliary strip portions 54 and 54' may be cutaway and removed. Similarly the web portions 56 may be severed orremoved to separate an individual LED assembly 63 together with thecorresponding lens 64.

As shown in FIG. 14, the encapsulant material 70 is provided with aconcave exterior surface 72 which is covered or coated by a reflectivematerial such as paint containing titanium oxide. As a result, aretroreflective surface is provided which appears convex to the diode 58and to the light emissions from the diode. The retroreflected emissionsare transmitted back through the encapsulant and are seen by viewing thelens through a convex outer surface 76 of the lens. The diode thereby ispositioned between the surfaces 72 and 76.

The surface 76 is flanked on either side by diagonally projectingsurfaces 78 which generally radially intersect the convex surface 76.The surfaces 78 provide additional retroflective surfaces for the LEDlight emissions and tend to conform or diffuse the light emissions intoa broad area stripe configuration distributed arcuately along the convexouter surface 76. This avoids the tendency of the light emissions toappear as a pinpoint. Also, the use of a frosted lens is avoided whichwould tend to reduce the intensity of the light. The retroreflectivesurface 74 tends to magnify the retroreflected light as well as theremainder of the light emitted from the diode such that the stripe oflight emissions along the convex surface 76 appears unusually bright.

FIGS. 15 and 16 illustrate another preferred embodiment according to thepresent invention whereby a pair of LED's 80 and 82 are sandwichedbetween overlapping portions 56 and 56' of a corresponding pair ofcontact fingers 50 and 50'. The diodes 80 and 82 are electricallyconnected to the contact portions 56 and 56', for example, in a manneras described with respect to FIG. 12. The diodes 80 and 82 are orientedsuch that each of the contact portions 56 and 56' is an anode lead forone of the diodes and a cathode lead for the other diode. Thus a voltageof a given polarity which is impressed across the contact portions 56and 56' will light only one of the LED's. Similarly, an impressedvoltage of an opposite polarity will light only the other LED. If theLED's 80 and 82 emit light of different colors, the polarity of thevoltage impressed across the contact portions 56 and 56' will beindicated by the corresponding color emitted by the only conducting LED.

What has been shown and described are preferred embodiments of thepresent invention. Other embodiments and modifications of the inventionwhich would be apparent to one having ordinary skill in the art isintended to be covered by the spirit and scope of the appended claims.

What is claimed is:
 1. A method for providing light emitting diodes withlenses and leads, the steps comprising:forming an opening in a strip ofelectrically conducting material, forming a pair of elongated leads froma portion of said material and extending from opposite sides of saidopening, forming from another portion of said strip a pair of resilientcontact fingers, each having one end secured to the end of thecorresponding lead adjacent the opening with the other ends of thecontact fingers biased against each other to provide a space outlined bysaid fingers, inserting a tool though said opening to move apart saidother end of each pair of fingers against their bias while said fingersare being carried by the strip, inserting a diode between said pair ofmoved apart fingers, removing said tool to permit said fingers to gripand suspend said diode over the opening, encapsulating said diodetogether with portions of said fingers in a light transmittingencapsulant material, and removing the remainder of the material of thestrip to permit isolation of the leads from each other.
 2. The method ofclaim 1 including prior to encapsulating, the steps of:locating saidgripped and suspended diodes and portions of said contacts incorresponding cavities of a light transmitting and rigid lens material,and filling said cavities with a light transmitting encapsulant materialto encapsulate said diodes together with said portions of said contacts.3. The method of fabricating a light emitting diode assembly, comprisingthe steps of:forming metal strip means with a plurality of electricalleads from a carrier strip, bending portions of said leads to projectoutwardly from said strip, arranging two sections of said strip means toprovide interengaged pairs of said bent lead portions with overlappingportions forming opposed contacts, said pairs of leads being resilientand tending to return to the original unbent orientations after beingbent, wherein said corresponding pairs of the overlapping portions areresiliently biased toward each other, deflecting apart correspondingpairs of contacts while being carried by a corrresponding portion ofsaid strip means, inserting an LED between each pair of deflected apartcontacts and removing the deflection forces, thus resiliently grippingeach said LED with said corresponding pair of opposed contacts,electrically connecting said opposed contacts to each said LED,inserting each said LED and portons of said contacts in a transparenthousing, and imbedding each said LED and portions of said contacts byencapsulant material internally of said housing, and covering said outerconcave surface of said encapsulant material adjacent the open end ofthe housing with a reflective material.
 4. A method for providing lightemitting diodes with lenses and leads, the steps comprising:forming anopening in a strip of electrically conducting material, forming a pairof elongated leads from a portion of said material and extending fromopposite sides of said opening, forming from another portion of saidstrip a pair of resilient contact fingers, each having one end securedto the end of the lead adjacent the opening with the other ends of thecontact fingers biased against each other to provide a space outlined bysaid fingers, providing a tool for moving apart said fingers againsttheir bias, properly registering a diode on said tool, inserting saidtool with said diode thereon through each of said openings to move apartsaid other end of each pair of fingers against their bias while saidfingers are being carried by the strip, positioning said registereddiode while on said tool between said pair of moved apart fingers,removing said tool to permit said fingers to grip and suspend said diodeover the opening, encapsulating said diode together with portions ofsaid fingers in a light transmitting encapsulant material, and removingthe remainder of the material of the strip to permit isolation of theleads from each other.
 5. The method of claim 4 including prior toencapsulating, the steps of:locating said gripped and suspended diodeand portions of said contacts in corresponding cavities of a lighttransmitting and rigid lens material, and filling said cavities with alight transmitting encapsulant material to encapsulate said diodestogether with said portions of said contacts.
 6. The method offabricating a light emitting diode assembly, comprising the stepsof:forming metal strip with a plurality of electrical leads from acarrier strip, bending portions of said leads to project outwardly fromsaid strip, arranging two sections of said strip to provide interengagedpairs of said bent lead portions with overlapping portions formingopposed contacts, said pairs of leads being resilient and tending toreturn to the original unbent orientations after being bent, wherebysaid corresponding pairs of the overlapping portions are resilientlybiased toward each other, providing a tool for deflecting apartcorresponding pairs of contacts, properly registering an LED on saidtool, deflecting apart corresponding pairs of contacts with said toolwith said properly registered LED thereon, while said contacts are beingcarried by a corresponding portion of said strip, inserting said LEDbetween each pair of deflected apart contacts and removing thedeflection forces, thus resiliently gripping each said LED with saidcorresponding pair of opposed contacts, electrically connecting saidopposed contacts to each said LED, inserting each said LED and portionsof said contacts in a transparent housing, and imbedding each said LEDand portions of said contacts by encapsulant material internally of saidhousing, and covering said outer concave surface of said encapsulantmaterial adjacent the open end of the housing with a reflectivematerial.